Method and apparatus for spinning artificial filamets



Nov. 16, 1948. v H, FURNESS 2,453,839

METHOD lAND APPARATUS FOR SPINNING ARTIFICIAL FILAMENTS IN VEN TOR.

Nov. I6, 194s.v w. Hf FuRNl-:ss' 2,453,839 I METHOD ANI) APPARATUS FOR SPINNING ARTIFICIAL FILAMENTS Filed Dec. 15, 1945 2 Sheets-Sheet 2 MATERIA L IU Patented Nov. 16, 1948 METHOD AND APPARATUS FOR SPINNING l ARTIFICIAL FILAMENTS William H. Furness, Haddonfield, N. J., assigner to American Viscose Corporation, Wilmington, Del., a corporation of Delaware Application December 13, 1945, Serial No. 634,752

' (ci. is-s) 19 Claims.

This invention relates to the spinning of articial filaments and is particularly concerned with a method and apparatus for imparting twist to a plurality of filaments near the position of original filament formation.

Heretoiore, it has been attempted to twist the filaments formed by a spinneret by rotating the spinneret about its axis so that the bundle of lilaments proceeding therefrom in the coagulating medium was twisted about its axis. the twist occurred immediately at or near to the spinneret so that it was extremely difficult to rotate the spinneret at any substantial speed without completely disrupting the material form ing the filaments as they leave the spinneret. Such attempts have also been accompanied with attempts to rotate the coagulating medium with the spinneret about the axis of the spinneret. In such systems heretofore proposed, it has been impossible to maintain the rotation of the coagulating medium suilciently close to the speed of rotation of the spinneret to prevent the development of extreme turbulence and a strong force or forces tending to shear the stream of lamentary material right at the point of discharge from the spinneret face. It has also been suggested to prevent twisting andV shearing at or near the spinneretface by directing the laments proceeding from the rotating spinneret through the rotating coagulating medium to a guide in the medium which guide is oliset from the axis of rotation and rotates at the same speed as the spinneret about the axis., Even in this system, great difculties are encountered in respect to the prevention of excessive turbulence of the coagulating medium and the Icontrol by the guide Adepends upon the exertion of frictional forces which are detrimental to the filaments being twisted as they pass through the guide. i

The present invention provides an improved method and apparatus for twisting laments near the point of their formation which reduces to a minimum the development of turbulence inthe coagulating medium. It also hasthe advantage of twisting the filament bundle at a region spaced a substantial distance from the spinneret but depends upon uid forces within the coagulating medium for preventing the twisting zone from backing `up entirely to the spinneret. Besides these primary objects of the invention, other ancillary objects, such as the provision of a-readily laced form of equipment for executing the new process, and other ancillary advantages will be apparent from the drawing and the description thereof hereinafter. l

In general,

In the drawing, which is illustrative of preferred embodiments of the invention,

Figure 1 is a side elevation, partly in crosssection, showing one system for carrying out the invention,

`Figure 2 is an end View looking toward the left end of the apparatus shown in Figure 1,

Figure 3 is a transverse section on the line III-III of Figure 1,

Figure 4 is a transverse section taken on line IV-IV of Figure 1,

Figure 5 is a detail section taken on line V-V of Figure 1,

Figure 6 Ais an elevation partially in cross section, showinganother embodiment, and

` Figure '7 is a perspective view of .the guide shown in Figure 6.

In general, the invention involves the rotation of the laments and the coagulating medium through whichthey pass about a common axis which is offset from the path of the filaments through the greater length of the body ofthe bath and which is eccentric of the body'of the bath. This causes the portion of the coagulating medium through which the filaments proceed as they pass between the spinneret and the discharge to rotate substantially in unison with the laments up to the point of discharge. This motion prevents the development of turbulent forces in the medium adjacent the path of the filaments and likewise tends to keep the twisting point nearer the position of lament discharge from the body of the coagulating medium than the spinneret. l

Referring to Figures 1 to 5, a suitable form of apparatus for producing twisted ilaments Iin ac-` cordance with the present invention is shown and comprises a, coagulatlng medium receptacle 2 which is carried by a supporting saddle 2a provided with a projecting sleeve 3 rotatable in suit able spaced bearings 4 and 5. A pulley 6 driven by a belt l and a motor or equivalent driving means (not shown )serves to rotate the system. The coagulating medium receptacle 2 may con veniently comprise two members 8 and 9 each having an overall cross section of generally semicircular shape. The member 8 is provided with a longitudinal channel l0 for receiving the coagulating medium. The channel I0 may occupy the entire cross section of the semicircular member 8 except of course for the outer wall. However, it is preferred that the channel have a compact cross section, such as that of a square, rectangle, arcuate-bottomed, parallel-sided quadrilateral Shown particularly in Figure 4, and preferably,

as shown, the lateral surfaces of the channel are disposed about an intermediate plane of symmetry in which the axis of rotation lies. This provides for the maximum economy of liquid, the smoothest flow thereof through the channel and a minimum of turbulence.

The channel IU is provided with ra supporting bracket II adapted to receive the duct I2 for feeding spinning material to the spinneret I3. Near the other end of the channel ID a barrier wall I5 is provided. This wall'v I4 ,is spaced from the adjacent wall of member 9 to provide a discharge outlet for the filaments and coagulating medium. The member 8 may have a longitudinal recess or groove I5 adapted to4 receive a sealing gasket I8 and a complementary longitudinal projecting tongue portion Il of the-.memberl which may be a solid block of a suitable weight to properly balance with the coagulating medium-containing member 8 during rotation of the assembled unt. The member 9 maybe hinged at I8.

The U-strap I9 secured to member-'8 is provided with-a slot 2U (see Figure 5) and a key 2I having a foot 22 extends through a suitable bore in member 9 and the slot 23 of the strap I9. The key terminates in a yoke '23 pivotally carrying a toggle lever 24. The cam'25 of the toggle lever Works within a transverse groove`26 in the member 9. In the position shown in Figure 1, the

toggle lever 2li is in locking position with the cam engaging the groove 26 tightly. In thisposition, the foot 22 is set atan angle to the slot 28 as shown in Figure 5. By lifting the handle of lever 24, the cam 25 is freed from the groove 25 and the key may be rotated so that its foot 22 is in registry with the slot 20 to thereby allow release of the member l9 for swinging freely on its hinge I8. A gasket or packing V2'! may be 4provided to seal the key 2I.

vMember 8 carries adjacent its discharge end a projecting sleeve 28 having a passage '23 for guiding the twisted filaments discharged from the device. The sleeve 28 may be rotatably supported in the bearing 30. Between thev member 9 and the sleeve 28 there is provided a gasket 32 of semicylindrical shape which serves to prevent discharge of liquid. Gasket-32 may be formed as van integral part of gasket I6. lThe bearing carries a splash guard -33 which surrounds'the vdischarge end of the coagulating receptacle2.

This guard serves to catch coagulating medium discharged through the passage 34 extending between wall I4 and the inwardly extendingportion of sleeve 2B. The guard is also provided with an inwardly turned deflecting ring 35 to catch liquid thrown to the upper 'portion of guard'33 and tending to` flow down the conical skirt of the guard. The guard 33 is provided with a discharge outlet 36 and liquid flowing therethrough maybe deflected to any suitable drainl or recovery system not shown by the plate 31. The guard 33 as shown in Figure 2, maybe of hinged construction, the wing nut SI serving to releasably secure the two hinged parts together.

The coagulating medium may be introduced into. the device through any suitable means and conveniently it may be introduced through a sleeve 38 surrounding the axially extending portion I2a`of` the spinning material duct I2. The sleeve'33 may be rotated with the duct I2 and sleeve 3 and to assure the same speed of rotation, a seat 39 may be formed at the inner end of sleeve 38`for receiving the inclined portion of duct l2.

To lace up the embodiment shown in Figures 1 Vto 5, the operator, before starting rotation of ifo ' of cross currents and-turbulent effects.

4 the device, opens the hinged guard 33 and swings the member 9 upwardly on the hinge I8. He then draws the laments from the spinneret through -a sleeve 28, such as by means of a suction device, and carries the filaments to the next handling device such as a godet or thread-advancing re'el. .'Hefthereufpon secures member 9 into closed '-position, closes'the guard 33, and starts the motor for rotating the receptacle 2. This causes rotation of the coagulating medium in the-channel Ill and the filaments with it.

Since the-axis of rotation of both filaments and bath is offset from the path of the filaments through substantially the entire length of the coagulating medium, (except possibly adjacent the filament-discharge end thereof) the twist is put intothe. bundle of filaments in the passage 29 of sleeve 28 which rotates with the system.

Theflow of the coagulating medium is substantially concurrent with the travel of the filaments and the development of cross currents in the coagulating medium 4is minimized ybecause', of .the fact that centrifugal-force is the main forceexerted-uponthe medium. However, this ,force merely creates a pressure towardthevouter wall of member and a flow of the mediumaway from the spinneret `which is controlled "by'the end wall I4. This end wall Id'in effect maintains a predeterminedsurface lupon the body of coagulating medium when the ydevice lis rotating at sufficient-speed to Withdraw the liquid from the confining surface, such as ofthe gasket I3. Centrifugal force also tends to keep the-filaments well out 4into `the body of coagulating imedium throughoutfthe' length thereof, exceptnear the point-of ldischarge into' the passage 2S. Thev provision of Aa narrow channel' IU of compact'crosssection yfor the coagulatingmedium and filamentsalso serves to Vminimize-the development The system thus is so constructed as toassure that centrifugal force favorsa smooth -uniform concurrent flow of coagulating -medium and'filaments. The speed of rotation of this emboditment'shouldbe sufficient to Ymaintain la definite surface on the body of coagulating "medium 'turbulent or cross-current effects.

Figures 6l and'7 show-a modification arranged with the axis of rotation substantially vertical. Inthis embodiment, therotating receptaclemay comprise two halves'SaandSa secured' in-a cup 'bracketli which lhas a projecting sleeve" 3 correspondingto'that of Figure 1. The sleeve 3 is rotatable in a-suitable step bearing comprising elements 4 and 5 and maybe drivenl by a pulley 6 and belt 1, as in Figure 1.

As in Figure 1, the coagulating medium may be introduced through the space between the sleeve 38 and theV duct 12a which has the offset portion i2 terminating inthe spinneret I3. If desired, the spinneret I3 may have its face inclined from the horizontal as shown. This allows of the use of greater speeds of rotation Where the spinning material is of high specic gravity and would tend to be thrown out too rapidlylunder the influence of centrifugal force to escape breakage of filaments because of sharp deflection of the spinning material as it leaves the spinneret orices. The transverse cross section of the channel l0 may be substantially the same as that shown for the channel l0 in Figures 1 to 5 and it terminates in an end wall I4. However, in this embodiment, the end wall is spaced from the member 9a to provide an approximately axial discharge passage for the filaments and coagulating medium.

The coagulating medium flows radially outwardly over the top surface of the members 8a and 9a and over the ring 46 of flexible material, such as of rubber or synthetic rubber, into the guard 33a having a discharge 36a. The guard 33a may comprise an inside conical ring 4| to contain any liquids splashed back from the outer conical portion of the guard 33a. The guard 33a is carried by a bracket 42 which is slidably mounted in a pair of parallel guideways 43. The bracket 42 may also carry a stationary guide 44, more particularly shown in Figure 7. This guide may be formed of a suitable non-corrosive lowfriction metallic wire bent around into the form of an overlapped ring pigtail which is readily laced and which prevents the filaments from flying out of the ring during normal operation.

In this embodiment, rotation may be effected at any speed, even at speeds giving rise to insufficient centrifugal force to cause the formation of a vortex, i. e., insufficient to cause separation of a surface of the coagulating medium away from the confining surface 45 of member 9a. The operation is similar to that described for Figures 1 to 5 but lacing may be accomplished simply by allowing the lament-forming material to flow to the top of the receptacle 2. Lacing, of course, is performed with the guard 32a moved upwardly out of the way along guideways 43. This upward motion of the guard is permitted by virtue of the flexible ring 46 which allows passage both downwardly and upwardly of the deflector 4i within the guard 33a. Centrifugal force tends to hold the filaments away from the axis of rotation and tends to prevent the insertion of twist until the bundle approaches the guide 44, such action being the result of the Viscosity effects of the coagulating medium within the receptacle l0 as compared to that above such receptacle. When high speeds of rotation are involved, a vortex survface may be formed away from the upper portion of the confining surface 45, the distance along which such separation occurs depending upon this speed of rotation. However, this does not essentially disturb the uniform ow of coagulating medium with the lamentary material and as in the other embodiment, high speeds of rotation may be used without encountering serious cross current effects and the prevention of the backing up of the twist to the spinneret is under the control of the fluid medium rather than a mechanical element exerting frictional effects upon the lamentary material.

The invention is applicable to the production of artificial lamentary material of any character whatsoever by wet spinning methods. Examples are of the production of regenerated cellulose by extrusion of viscose through a spinneret into an acid or salt coagulating bath at temperatures from normal room temperature to about 50 C.; also, the production of regenerated cellulose laments from cuprammonium cellulose; the spinning of cellulose acetate, other cellulose esters as well as cellulose ethers and other derivatives;

the spinning of resinous materials, Vsuch as the 'vinyl resins, particularly copolymers of vinyl chloride with vinyl acetate or acrylonitrila nylons, vinylidene chloride, fluoride, or bromide; the spinning of proteinous materials such as casein; etc.

It is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined in the appended claims'.

I claim:

1. The method of producing articial filaments comprising extruding a filament-forming material through a spinneret directly into a body of a liquid coagulating medium to form a plurality of filaments proceeding therefrom in generally the same direction along a common path and rotating the filaments and the coagulating medium as the filaments proceed therethrough bodily about va common axis ofsetifrom the path of the filaments through the medium and eccentric of the body of liquid.

' 2. The method` of producing articial filaments comprising extruding a filament-forming material through a spinneret directly into a body of a liquid coagulating medium to form a plurality of filaments proceeding therefrom in generally the same direction along a common path and rotating the laments and the coagulating medium as the filaments proceed therethrough bodily about a common axis outside the body of the medium and eccentricof the body of liquid.

3. The method of producing artificial filaments comprising extruding a filament-forming material through a spinneret into a body of a liquid coagulating medium to form a plurality of filaments, rotating vthe filaments and the coagulatlling medium as the `filaments proceed therethrough about a common axis offset from the path of the filaments through the medium and eccentric of the body of liquid, removing the laments from the body of coagulating medium, and then passing the filaments through 'a confined guiding passage while rotating the confining surface thereof.

4. The method of producing artificial filaments comprising extruding a filament-forming material through a spinneret into a longitudinally flowing body of a liquid coagulating medium to form a plurality of filaments, rotating the laments and the coagulating medium as the filaments proceed therethrough bodily about a common axis offset from the path of the laments through the medium and eccentric of the body of liquid, substantially the entire body of liquid along at least the greater part of its lamencontaining length from the position of filamentextrusion being disposed on one side of the axis of rotation at any given instant.

5. The method of producing artificial laments comprising extruding a filament-forming material through a spinneret into a body of liquid longitudinally flowing in a narrow channel bounded by two opposed lateral surfaces having an intermediate plane of symmetry to form a plurality of filaments proceeding from the spinneret in generally the same directionalong a common path, and rotating the channel contain ingthe filaments and the bath about an axis eccentric of and outside the body of the medium disposed in the plane of symmetry with respect to the lateral surfaces.

6. Apparatus for spinning artificial ilaments comprising a receptacle for a coagulating liquid mounted yrotatably onv an axis, said receptacle nass-,ssa

comprisingfa .liquide-receiving channel i the i maior portion of which: is: disposed:I to.' one` side: of the axis of rot-ation; azspinneret arranged-.to deliverv aplurality of streams: of filamenteforming mate rial vinto the channel all onone side4 of. theaxis, means for supplying a coagulating liquid tothe channel, guidemeansfadjacentthe end. of the receptacle away fromnthe .spinneret .forfrreceiving the filaments discharged' from thezreceigntacle,l .and means for rotating the receptacle-.and spinneret about said axis.

'7. Apparatus for. spinning artificial laments comprising a receptacle: for. a coagulating; liquid mounted rotatably: on'v an. axis,` said receptacle comprising a i Milind-receiving channel. the. major portion of which is disposed to. one sideoffthe axis of rotation, aspinneret disposed in the channel away from the-axis of rotation tol deliver a plurality ofl streams .of lament-forming mate.- rial into the channel all on one side of. the axis, means for supplyinga coagulating liquid'to.- the channel, guide means adjacent the endof'the receptacle away fromzthe spinneret-for receiving the lamentsdischarged from the receptacle; and means for rotating, the receptacleand spinneret about` said axis.

8; Apparatus for spinning articial filaments comprising. afreceptac'le for afcoagulating liquid mounted rotatably onian axis, said receptacle comprising a liquidrreceivingchannel the major portion of which is disposed tov oneside of the axis oi rotation, said channel having a peripheral walland an end wall extending inwardlyl toward the axisof rotation but terminating short-ofithe axis to providea passagev for' discharge of the filaments, a spinneret disposed in the` channel away fromthe -axisof'rotation to -del-iver af pluralityof streams of ilamentfiorming material into the .channel allononeside or" theaaxis, means forsupplying acoagulating liquid vto the. channel, guide means adjacent the-endof the receptacle away from the spinneret for receivingvthellaments discharged from the receptacle, and means for rotating thereceptaclefand .spi-nneret about said axis.

9. Apparatus for spinning artificial filaments comprising a receptacle for a coagulating liquid mounted rotatably on an axis, said receptacle comprising aliquid-receiving channel the major portion of which is disposed to oneside yof the axis of rotation, said channel having a peripheral wall-.zandzan end'wall extending, inwardly toward the axis of rotation but terminating short of the axis to provide a passage for discharge of the laments, a spinneretdisposed in the channel away 'from the axiscf rotation to deliver. a plurality of. streams of filament-forming, material into the channel all. on one side of the axis, means for supplying a coagulating liquid-to theV channel, guide means adjacent .the end ofthe receptacle away fromthe spinneret for receiving the filam ments discharged from thev receptacle, andmeans for.: rotating the receptaclaguide means, and spinneret ,about said' axis;

10; Apparatus for spinningt articialfilaments comprising a .receptacle for azcoagulating; liquid mounted rotatably onr anf axis, said receptacle comprising. two separablemembers Oneonly'of which is provided: with a liquid-receiving channel the major portion ofiwhich is disposedstov one side of the'axis ofirotation, aspinneret arranged to deliver a plurality of streams of: lamentforming materialinto the'channel all on one side of the` axis, v.means for. supplying s. a: coagulating liquid to: the. channel, guide: means. adjacentthe end; of-rthea receptacle? away fronrthe; spinneret fora' receiving:I the laments discharged." from: the receptacle,` .and :meanszfor rotating: the receptacle Spinnerei; about: said axis'.-y

l i. ,Apparatus for: spinning artificial filaments comprising. a: receptaclev for a .coagulati-ngg. liquid mounted. rotatably on an. axis, said receptacle `comprising two separable members Ahinged to each other, onel onlyofJwhich isprovidedwwith a. liquidreceiving s channel theA major: portion of 1 which. is disposed to one side of the axis or" rotation, a spirmeret4 arranged to deliver a plurality' of streams-of lamentforming material into the channelall' ononee side'of the axis, means for supplying 'a' ccagulating` liquid to the: channel, guideemeans adjacent the-end of the receptacle away' from thespinneret for receiving the. rilanrents -idisc-harged .frorncthe receptacle, and meansv for: rota-.ting thereceptacle-*an'd spinneret' about said axis;

12. Apparatusfor spinning artificial ilaments comprisingl a receptacle for a .coagulating. liquid mounted' rotatablyr on anaxis, said receptacle comprisingA two. separableV members each having al generally; semicylindrical shape', one onlyv of thememberszhaying a longitudinal channel disposed entirely to one side of theaxisof rotation, said channel. having a: peripheral wall and an end. wall. extending. inwardly therefrom toward the: axiso rotation butfterminating: short of the axisfto. provide af. passage `forl discharge. of the filaments, a; spinneret disposedlin the lchannel away from the-axis of rotationto deliver a Iplurality of; streams-.of filament-forming material into the channel all. on one si-de of the axis, means for supplying azcoagulating'liquid tothe channel, guide means adjacentthe .end of the receptacle-awayA fromthe spinneret for receivingthe filaments dischargedA from the receptacle, and meansfor-'rotating-- the receptacle and spinneret about vsaid axis, therotating-.assembly beingsubstantially balanced. dynamically.

13..Apparatus' for spinning articial filaments comprising-.a 'rotatable` support,r a receptacle carriedby; said supportA for rotation-therewith, a spinneret in, the-receptacle, ay supply duct connected .to the spinneret and carriedby the suppprtfor: rotation therewith,v said :receptacle comprising two'complementary membersY each extending longitudinally from'a positioni adjacent thespnneret to va position away irornzthespinn-eret,l a longitudinal; channel provided in one of the members and the other having one surface facingfthe channel and enclosing-,one side of it, said latter member beingv pivotally mounted about anzaxis'transverse of the rotational axis of. thefreceptacle.

14; Apparatus,- for': spinning4 artificial filaments comprisingl arotatable. support, areceptacle .carriedz'by said-.supporti fory rotation therewith', a spinnereti'in the receptacle;A a..supplyN ductzcon nected tothe spinn'eret'and carried bythezsupportifor rotationltherewith, saidreceptacle com; prising twol complementary members-each extending.. longitudinally from a positionadjacent thef-spinner'et to a'- position away from the spin'- neret', azlongitudinal channel provided inl onel of theemeinbers andthe other having.' one surface iacingfthe channel and enclosing one'I side oilit, said latterlmember beingpivotally mounted about arr axis :transverse lofthe rotational'axi-s'of the receptacle;

l5?.l Apparatus-for' spinning `artificial filaments comprising raf rotatable support, areceptacle care ried byf said support; for'A rotation therewith, a

spinneret in the receptacle, a supply duct connected to the spinneret and carried bythe support for rotation therewith, said receptacle comprising two complementary members each eX- tending longitudinally from a position adjacent the spinneret to a position away from the spinneret, a longitudinal channel provided in one of the members and the other having one surface facing the channel and enclosing one side of it, said latter member being pivotally mounted about an axis transverse of the rotational axis of the receptacle, guide means adjacent the end of the receptacle away from the spinneret and axially disposed with respect thereto.

16. Apparatus for spinning artificial filaments comprising a rotatable support, a receptacle carried by said support for rotation therewith, a spinneret in the receptacle, a supply duct connected to the spinneret and carried by the support for rotation therewith, said receptacle comprising two `complementary members each extending longitudinally from a position vadjacent the spinneret to a position away from the spinneret, a longitudinal channel provided in one of the members and the other having one surface facing the channel and enclosing one side of it, said latter member being pivotally mounted about an axis transverse of the rotational axis of the receptacle, guide means adjacent the end of the receptacle away from the spinneret and axially disposed with respect thereto, means for rotating the guide means and receptacle together about their common axis.

17. Apparatus for spinning artificial filaments comprising a support rotatable on a horizontal axis, a receptacle carried by said support for rotation therewith, a spinneret in the receptacle, a supply duct connected to the spinneret and earried by the support for rotation therewith, said receptacle comprising two complementary members each extending longitudinally from a position adjacent the spinneret to a. position away from the spinneret, a longitudinal channel provided in one of the members and the other having one surface facing the channel and enclosing one side of it, said latter member being pivotally mounted about an axis transverse of the rotational axis of the receptacle.

18. Apparatus for spinning artificial filaments comprising a support rotatable on a horizontal axis, a receptacle carried by said support for rotation therewith, a spinneret in the receptacle, a supply duct connected to the spinneret and carried by the support for rotation therewith, said receptacle comprising two complementary members each extending longitudinally from a position adjacent the spinneret to a position away from the spinneret, a longitudinal channel provided in one of the members and the other having one surface facing the channel and enclosing one side of it, said latter member being pivotally mounted about an axis transverse of the rotational axis of the receptacle, guide means adjacent the end of the receptacle away from the spinneret and axially disposed with respect thereto.

19. Apparatus for spinning articial filaments compri-sing a receptacle for a coagulating liquid mounted rotatably on a vertical axis, said receptacle comprising a liquid-receiving channel the major portion of which is disposed to one side of the axis of rotation, a spinneret arranged to deliver a plurality of streams of filament-forming material into the channel all on one side of the axis, means for supplying a coagulating liquid to the channel, guide means adjacent the end of the receptacle away from the spinneret for receiving the laments di-soharged from the receptacle, and means for` rotating the receptacle and spinneret about their common vertical axis.

WILLIAM H. FURNESS.

REFERENCES lCITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,413,332 Hooper April 18, 1922 1,500,934 Hooper July 8, 1924 2,073,906 Sehrenk Mar. 16, 1937 2,241,304 Heywood et al May 6, 1941 FOREIGN PATENTS Number Country Date 111,325 Switzerland Apr. 16, 1924 431,681 France Sept. 18, 1911 

